The invention is concerned with a profiled bolt mounting unit for mounting on a structural member, comprising a blind rivet body having a sleeve and a flange for abutting against the structural member provided for mounting purposes with a mandrel having a setting head and a pull stem, which may be gripped by a setting tool and detached from the mandrel at a predetermined breaking point after exceeding a certain pulling force.
Such a profiled bolt mounting unit is known from German Gebrauchsmuster 80 00 891. Profiled bolt mounting units are, for example, used to replace a profiled bolt which has not been properly welded on in production or to replace a profiled bolt that has broken off during use. Furthermore, they can be used for mounting profiled bolts at places which are not suitable for conventional profiled weld studs to be welded on. This may arise, for example, when the structural member consists of a steel not suitable for welding, a non-weldable metal, plastics or similar material. On a known profiled bolt mounting unit, the blind rivet body comprising abutting flange and sleeve as well as the profiled bolt portion are designed in one piece. The mandrel is pushed through the sleeve and through the profiled bolt portion, which for this purpose must have a suitable bore, and a predetermined breaking point is provided within the sleeve between the setting head and the stem. This device has the disadvantage, that a bore has to be provided passing through the blind rivet body and the profiled bolt portion to accommodate the mandrel needed for mounting. The manufacture of the blind rivet body consisting of rivetable metal having a through-bore and flange projecting away from the sleeve with adjacent profiled portion is very costly. Moreover, the bore in the profiled bolt portion considerably reduces the strength of the unit, particularly with respect to a bending moment stress. Furthermore, with this mounting unit being designed in one piece, the choice of material for the profiled bolt portion is very limited, since the material has to be selected so that deformation of the sleeve by the setting head is possible.
In DE-OS No. 33 41 266 is described a blind-rivet-like expansion plug for securing a bracket to masonry, on which is provided a grooved stem portion forward of the predetermined breaking point for checking the anchorage after completion of the riveting process. The predetermined breaking point and the grooved stem portion are located before the setting process within the sleeve of the blind rivet and are dimensioned so that the grooved stem portion projects slightly beyond the flange of the blind rivet sleeve after setting so as to allow the supervision of the setting process and an axial interlocking means, which consists of a compression ring presses onto the grooved stem portion. Since the grooved stem portion is entirely within the rivet sleeve, it is not possible to roll this portion after assembly of the expansion plug. In addition, the outside diameter of this portion has to be significantly reduced in relation to the inside diameter of the rivet sleeve in order to permit a satisfactory sliding movement of the portion inside the rivet sleeve. The fixing effect is exclusively attained by clamping the material between the flange of the rivet sleeve and the shank of the rivet sleeve. Significant axial forces and/or bending moments cannot be absorbed by the grooved stem portion.
Furthermore, from DE-PS No. 449 475 is known a hollow-rivet-like fastening element for tightly fastening two panels, on which the hollow rivet, together with a mandrel, is pushed through bores of the panels aligning with one another. The leading end of the mandrel is provided with a cone, which projects slightly from the leading end of the hollow rivet, but with its largest diameter kept smaller than the diameter of the bores. For setting, the hollow rivet a nut is screwed onto a thread of the mandrel at its end opposite the cone, which turns over the respective end face of the hollow rivet, by which the cone drawn into the other side of the hollow rivet also turns over on this side. In this way a flange is produced on both ends of the hollow rivet. The mandrel with nut remains thereby in or on the hollow rivet in order to arrest the mandrel inside the hollow rivet and to ensure the tightness of the assembled panels. This fastening method thus does not relate to a blind rivet having mandrel and predetermined breaking point, so that DE-PS No. 449 475 does not provide any reference to a construction involving a blind rivet.
It is an object of the present invention to provide a profiled bolt mounting unit, which can be easily mounted, simply manufactured and exposed to higher strength.